The present disclosure relates to a sewage/wastewater treatment system using granular activated sludge and a membrane bio-reactor and a sewage/wastewater treatment method using the same that are configured to effectively remove pollutants contained in raw water through a granulation tank in which the granular activated sludge is contained and to allow the raw water to be filtered through movable membranes located on the upper portion of the granulation tank, thereby conducting advanced water treatment for tap water for miscellaneous.
Generally, an activated sludge system, which is commonly used as biological sewage/wastewater treatment equipment, needs an aerobic tank for oxidizing organic matters by using floating microorganisms and a secondary clarifier for conducting solid-liquid separation so that treated water is separated from the floating microoragnisms.
However, the facility for the secondary clarifier is complicated in the mechanical device thereof, sensitive in the hydraulic load thereof, and causes various problems like sludge rising, and recently, accordingly, a variety of water treatment technologies wherein membranes are submerged in the aerobic tank using the activated sludge system (which is called a membrane bio-reactor MBR) have been developed and suggested.
The MBR system is configured wherein water treatment is conducted with a single or continuous modified activated sludge processes so as to effectively remove the pollutants contained in sewage and wastewater, and in this case, microfiltration MF membranes or ultrafiltration UF membranes are used as physical barriers for complete solid-liquid separation. The UF and MF membranes are submerged in the interior of the bio-reactor or in the exterior of the bio-reactor.
If the membranes are submerged and operated for the replacement of the clarifier in the activated sludge system, however, the activated sludge may be broken by means of the sticky characteristics thereof and the aeration, and thus, the surfaces of the membranes may be clogged with the fine particles of the activated sludge, so that the membranes should be often cleaned. Due to the clogging of the membranes, accordingly, there are many difficulties in actually applying the membrane bio-reactor to the water treatment system.
So as to prevent the membranes from being clogged due to the broken activated sludge, there is a sludge granulation method using self-granulation characteristics of microorganisms. Representatively, there are an upflow anaerobic sludge blanket method conducted through upflow under an anaerobic condition and a granulation method conducted under an aerobic condition. Now, the granulation method under the aerobic condition will be in detail explained.
If the microorganisms of the aerobic tank for the activated sludge are contacted with each other at a slow speed by means of an agitator, the contacts between the activated sludge are generated by means of the bridge reaction of the activated sludge to allow the activated sludge to bind with each other, so that the activated sludge becomes granulated through self-granulation thereof, without having any media, and the granular activated sludge is excellent in the submerging capability and compact in size, thereby reducing the volume occupied by the reactor tank and requiring no clarifier.
The activated sludge granulation device largely includes an indirect aeration tank and a granulation tank, wherein the indirect aeration tank introduces water from the upper portion of the granulation tank, excessively aerates the water introduced thereinto, and introduces the water in which dissolved oxygen is abundant into the granulation tank, as upward flow, so as to allow the sludge in the granulation tank to be maintained in an aerobic condition, and the granulation tank is adapted to allow the contacts between the sludge to be generated through the vortexes caused by the hydrodynamic force generated from the indirect aeration tank toward the granulation tank or through an agitator disposed in the granulation tank.
A sewage/wastewater treatment systems and methods using granular sludge is disclosed in Korean Patent No. 1336988 (issued on Dec. 5, 2013), and the system is configured wherein anaerobic granular sludge, first aerobic granular sludge, second aerobic granular sludge and nitrification granular sludge are injected correspondingly into an anaerobic tank, anoxic tank, a first aerobic tank and a second aerobic tank, each of them having a separation plate, thereby greatly improving the treatment efficiencies of the pollutants such as organic matters, nitrogen, phosphate and so on in the sewage and wastewater.
However, the conventional system is configured to allow the treated water to pass through a clarifier in which membranes are additionally disposed to separate and discharge the floating microorganisms contained in the treated water passing the aerobic tank, thereby disadvantageously increasing the installation area and requiring separate facilities such as an air collection device, a pump, and a pipe for cleaning the membranes.